Field of the Invention
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to an interlock fir an enclosed electrical switching apparatus.
Background Information
Electrical switching apparatus used in power distribution systems are often mounted within a switchgear enclosure either individually or in combination with other switchgear (e.g., without limitation, circuit switching devices and circuit interrupters such as, but not limited to, electrical switching apparatus, contactors, motor starters, motor controllers and other load controllers). That is, the enclosure includes a number of sidewalk and a movable door defining an enclosed space.
Some electrical switching apparatus such as, for example, some medium-voltage and low-voltage electrical switching apparatus, can be relatively large. In order to facilitate movement (e.g., installation; removal; maintenance), such electrical switching apparatus are commonly coupled to draw-out mechanisms which permit such electrical switching apparatus to be drawn out of the switchgear enclosure. Accordingly, such electrical switching apparatus are commonly known in the art as “draw-out” electrical switching apparatus. The electrical switching apparatus may be further supported within a draw-out frame, commonly known in the art as a cassette or chassis. The draw-out mechanism includes, for example, a combination of rails and rollers coupled to one or the other, or both, of the sidewalls of the cell and the sides of the corresponding electrical switching apparatus and/or cassette, which is to be drawn into and out of the cell.
To reduce the chance of injury or damage to the electrical switching apparatus, the enclosure typically includes a “door-switch” interlock. Generally, an interlock is used to prevent a certain action when a device is in a selected position or configuration. As used herein, an “[X]-[Y] interlock” means that element [X] is locked when element [Y] is in a potentially hazardous configuration. Thus, a “door-switch” interlock is structured to, and operates on a principle of, locking the enclosure door when the electrical switching apparatus is energized. That is, when the electrical switching apparatus is energized, the enclosure door is locked in a closed position thereby preventing a user from removing the energized electrical switching apparatus.
Such door-switch interlocks have several disadvantages. For example, a door-switch interlock does not prevent the electrical switching apparatus from being energized once the door is opened. That is, a user may de-energize the electrical switching apparatus, open the door, then re-energize the electrical switching apparatus leaving the user exposed to an energized assembly. Further, interlocks often utilize rotating elements that are subject to wear. That is, a rotating element is disposed in a bearing or bore that wears, thereby allowing the rotating element to become misaligned. Interlocks, especially interlocks with multiple functions, are complex assemblies that are expensive and time consuming to install and are subject to degradation. That is, a combined switch-door interlock assembly/door-switch interlock assembly includes components that both lock the switch when the door is in a specific configuration and lock the door when the switch is in a specific configuration. Such a combined switch-door interlock assembly/door-switch interlock assembly may have one interlock wear down and need to have both interlocks replaced due to their combined nature. Further, interlocks also are often built into a cassette; that is, such interlocks are not able to be added to a cassette at a later time. Interlocks may also include electrical components, such as, but not limited to position sensors, that are not operable when de-energized.
There is, therefore, a need for an interlock structured to overcome these disadvantages as well as other. There is a further need for an interlock structured to operate with enclosures, cassettes and other hardware presently in use.